Our goal is to define how pro-inflammatory cytokines and factors derived from toll-like receptor (TLR) stimulation impact specific CD4 T cell immunity in vivo. Characterizing this process will improve adjuvant development by defining new methods to control in vivo T cell responses while minimizing toxicity. This goal is based on our recent work which unveiled an unexpected division of labor between the TLR4 adaptors. One path signaled T cell effector differentiation and homing to solid organs, and the other path was responsible for clonal expansion and inducing cell survival. Therefore, uncovering how the adjuvant response emanating from the TLR4 pathway affects T cell behavior will allow vaccinologists to push desirable effects on Ag-specific CD4 T cells. This goal will be accomplished in 3 specific aims by determining the mechanism of how each adaptor impacts T cells. In Aim 1 we will determine how TRIF controls T cell effector differentiation and homing by examining an innate cytokine axis that we hypothesize potentiates both cell behaviors. Data from this aim will help design vaccine formulations that will aid in driving effector T cell migration to specific sites of the body. In Aim 2 a proteomic map of specific CD4 T cells destined to survive will be captured and contrasted to the same specific T cells programmed to die. We will accomplish this goal using an innovative liquid fractionation approach that will permit us to mine the proteome for differential changes between these populations. Aim 3 will capitalize on our novel finding demonstrating that Ag-experienced CD4 T cells can facilitate adjuvant toxicity. We will define this process and develop new approaches to counter toxicity while promoting strong adjuvant responses. Thus, the results from this proposal will provide an adjuvant to toxicity ratio that can be used to gauge the effectiveness and safety of TLR agonists, and importantly provide an evidence-based approach to designing adjuvant therapeutics.